1. Field of the Invention
The invention relates to a fuel injection valve for the intermittent injection of fuel into the combustion space of an internal combustion engine.
2. Discussion of the Background
EP-B-0 228 578 describes a fuel injection valve with an injection valve member which is guided longitudinally displaceably in a housing in a bore extending in the direction of the longitudinal axis of the housing. This bore, which is connected via a throttle to a fuel high-pressure connection and is designed as an accumulator space, is closed off, at one end, by a seat for the injection valve member, said seat being provided with injection orifices, and, at the other end, by a cylindrical end piece which is guided in the housing by means of a narrow guide performing a sealing function. The end piece serves as a narrow sliding guide for a piston which forms part of the one-piece injection valve member. The injection valve member is narrowly guided in a further guide in the vicinity of the seat. The movement of opening and closing the injection valve member is controlled by controlling the pressure in a control space above the piston of the injection valve member.
As mentioned, the two guides for the one-piece injection valve member a produced in the form of narrow sliding fits, which means that these guides have to be accurately oriented axially, so that no lateral forces are exerted on the injection valve member, which could cause distortion of the latter, severe friction or even jamming and would impair the functioning of the fuel injection valve. The fuel injection valve is consequently complicated to manufacture and assemble. Moreover, the housing has a relatively large cross section, because, as mentioned, the central bore is designed as an accumulator space, this being a disadvantage for installation in internal combustion engines.
A generic fuel injection valve of the type initially mentioned is known, for example, from EP-B-0 686 763. In this fuel injection valve, the opening and closing movement sequence of an injection valve member installed longitudinally adjustably in a housing is controlled by means of a control device comprising a control piston which is a component separate from the injection valve member and operatively connected to the latter. Between the end face of the control piston and a control body fixed to the housing is located a control space which is delimited radially by a control sleeve. The control sleeve is arranged displaceably and with a narrow sliding fit in a housing bore receiving the control device. The control piston is likewise guided with a narrow sliding fit in the control sleeve. High-pressure supply lines are arranged parallel to the housing bore, in which the control device is accommodated, in the housing and are connected to a fuel high-pressure connection. One high-pressure supply line leads to the control device, the control space being connected to this high-pressure supply line via an inlet throttle connection. By an outlet orifice in the control body being opened or closed (by means of a controllable pilot valve), the fuel control pressure in the control space, which acts on the control piston, is capable of being controlled. The other high-pressure supply line leads to an annular space and to injection orifices of a valve seat element arranged at the lower end of the fuel injection valve. The injection valve member is accurately guided in a bore of the valve seat element by means of a component which is arranged above the annular space and on which the fuel system pressure acts from below.
So that the high-pressure supply lines can be accommodated in the housing, the latter must have a relatively large cross section, and this proves to be a disadvantage for installation in internal combustion engines on grounds of space.
The housing bore, in which the multi-piece injection valve member runs, is connected in this middle part to a fuel return line. This means that a low fuel pressure prevails in this region of the housing bore. This leads to leakages out of the adjoining regions, in which the fuel high pressure prevails, into this low-pressure region of the housing bore.
The object on which the present invention is based is to provide a fuel injection valve which is simple and cost-effective in terms of manufacture and assembly, in which at most insignificant leakages occur and which, even in its external shape, is advantageous for installation in internal combustion engines.
This object is achieved, according to the invention, by means of a fuel injection valve having the features of the independent claims set forth herein.
The fuel injection valve according to the invention not only has a simple and cost-effective makeup. Its special advantages are also that functional identity can be achieved in a simple way in all the valves of an internal combustion engine, since, in all components, the tolerances as regards both manufacture and assembly can be adhered to without difficulty. Dispensing with lateral high-pressure supply lines in the housing makes it possible to have a slender configuration of the fuel injection valve, this being advantageous for installation in internal combustion engines. The central bore which is located in the housing and in which the fuel high pressure prevails forms a completely leaktight region, so that leakages into spaces with lower pressure are virtually eliminated.
Preferred developments of the fuel injection valve according to the invention form the subject-matter of the dependent claims.
A fuel injection valve of the type initially mentioned, with a particularly preferred embodiment of the control device, forms the subject-matter of the independent claim 20.